Impact cylinder

ABSTRACT

A pneumatic impact cylinder with a piston latch operable to restrain the piston until predetermined pressure develops on the side of the piston associated with generating impact movement, the said latch being operable to release said piston in direct response to the said pressure.

United States Patent [72] Inventor Stanley Joseph Michalak 9231 S. CedarDrive, West Olive, Mich. 49460 [21] Appl. No. 806,551 [22) Filed Mar.12, 1969 [45] Patented June 1,1971

[54] IMPACT CYLINDER 5 Claims, 23 Drawing Figs.

52] us. Cl 91/45,

I 92/24, 92/135 [51] Int. Cl FISb 15/26 [50] Field ofSearch 91/45,41,

- [56] References Cited UNITED STATES PATENTS 2,360,535 10/1944 Ashton91/44 Primary Examiner-Martin P. Schwadron Assistant Examiner- Irwin C.Cohen Attorney-Glenn B. Morse ABSTRACT: A pneumatic impact cylinder witha piston latch operable to restrain the piston until predeterminedpressure develops on the side of the piston associated with generatingimpact movement, the said latch being operable to release said piston indirect response to the said pressure.

INVENTOR ATTORNEY Fig. 3

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Stanley J.Micho ATTORNEY PATENTEU JUN H97l 558L625 I35 HIM Fig. 20 i!! F'9- 23 MENTOR Stanley J. Michuluk BY H. 4

ATTORNEY IMPACT CYLINDER BACKGROUND Pneumatic impact cylinders have awide variety of uses. Essentially, they are fast-acting air cylindersthat deliver a hammerlike blow, and they are often used as actuators forsmall dies and special machinery. It is common practice to design thesepiston-cylinder assemblies with one end of the cylinder open, so thatthe impact velocity of the piston is not opposed by a mass of airentrapped ahead of the piston during the course of its movement. Thisarrangement necessarily eliminates the possibility of an effectivepneumatic retracting motion of the piston, which would be very useful inthe stripping" movement of a die to which the cylinder mechanism wasconnected. Quite commonly, a blanking action in which a-hole is punchedin sheet metal requires a forcible withdrawal of the punch out of thehole, and this is very difficult to provide in an open end impactcylinder without the use of an auxiliary cylinder for generating thewithdrawal action. The application of vacuum in place of impact pressureis normally not sufficient to generate the necessary forces, and alsotends to produce a slamming action which is undesirable.

In addition to the problem of pulling the cylinder back after thedelivery of the impact blow, the problem associated with the flow of airthrough relatively small conduits and orifices produces a throttlingaction which makes it very difficult to generate a high-rspeed pistonmovement through the use solely of a valve-controlled air admission.Means have been devised in the past for restraining the movement ofpiston until sufficient piston forces developed 'to overpower therestraint, and permit the piston to proceed on its impact blow. Thisarrangement thus permits a considerably amount of pressure to develop inthe cylinder prior to the release of the piston, so that the pistonvelocity can be generated by expansion of the compressed air, ratherthan relying solely on rapid admission of the air into the cylinder.These restraint devices that operates on the principle of a thresholdpiston force are subject to variations in performance, and do not havethe safety factors characteristic of a positive restraint under thedirect control of air pressure.

. SUMMARY OF THE INVENTION The present invention provides a releaseaction generated directly by the pressure within the cylinder, whichwill ultimately be used to at least assist in inducing the impact motionof the piston. In the preferred form of the invention, a heavy spring isalso utilized to produce this movement, the spring being compressed bypressure on the opposite side of the piston. The release of the latch isinduced by the movement of a small latch piston which is maintained inlocking position by the action of a special spring. The adjustment ofthis spring establishes the threshold pressure at which the latchoperates to retract a group of detents normally in engagement with ashoulder on an inside surface of the main impact piston. The generationof theradial detent movement from locking to released positions isproduced by the axial movement of the latch piston in cooperation withthe interengagement of inclined surfaces on these members, thusconverting the axial movement of the piston to radial movement of thedetent elements. In the preferred form of the invention, the pressurewhich induces the withdrawals of the detents will also control a valveon the opposite side of the main piston to move it to full exhaustposition, in order to minimize the resistance ahead of the main pistonduring its impact motion.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of an impactcylinder embodying the present invention.

FIG. 2 is a sectional elevation along the axis of the cylinder assemblyshown in FIG. I, in the extended position of the piston rod.

FIG. 3 is a sectional elevation similar to FIG. 2, with piston rodretracted.

FIG. 4 is an axial section on an enlarged scale showing the piston latchin the retracted condition. FIG. 5 is a section similar to FIG. 4, withthe piston latch in locking position.

FIG. 6 is a perspective view of the latch piston.

FIG. 7 is a perspective view of the detent assembly associated withFIGS. 4 and 5.

FIG. 8 is a section on the'plane 8-8 of FIG. 2.

FIG. 9 is a section on the plane 9-9 ofFIG. 3.

FIG. 10 is a section on the plane 10-10 of FIG. 2.

FIG. 11 is an end view of the cylinder illustrated in FIG. I.

FIGI 12 is a perspective view of the control piston shown in FIG. 10. I

FIG. 13 is an end view of the control piston shown in FIG. 12.

FIG. I4 is a section on the plane 14-14 of FIG. 12.

FIG. 15 is an axial section of a modified form of the invention, withthe main piston in position to project the piston rod.

FIG. 16 is a section similar to that of FIG. 15, with the piston at theopposite extreme of travel, corresponding to a retraction of the pistonrod;

FIG. 17 is a perspective view of the stem of the piston latch vassembly.

FIG. 18 is a perspectiveview of the latch piston associated with theFIG. 15 assembly, 7

FIG. 19 is a perspective view of the detents associated with the FIG. 15assembly.

FIG. 20 is a perspective view, partially in section, showing the cupunit of the FIG. 15 piston latch assembly.

FIG. 21 is a perspective view, partially in section, of the adjustingcap of the FIG. l5.assembly.

FIG. 22 is a perspective view ofthe rotary valve plate.

FIG. 23 is a perspective view of the cylinder head adjacent the valveplate in the FIG. 15 assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The impact cylinder assemblyillustrated in FIGS. 1 through 14 includes the cylinder heads and 31interconnected by the cylinder sleeve 32, with the heads being securedtogether by the rods 3336. Each of these rods traverses the heads, andis secured by nuts as shown at 3744. A piston rod traverses the head 30,and the extreme end of this piston rod will normally be connected to themoving section of a die, or some other actuated machine component. Theforces delivered by the piston rod will include the inertia effect ofthe piston 46, together with the effect of air pressure within thechamber 47 defined by the sleeve 32 on the right side of the piston, asshown in FIG. 2, and also the force of the spring 48. The inertia effectof the piston 46 (together with that of the rod 45) will be due to animpact velocity generated by the combined effect of the air pressure andthe compression spring 48. This spring moves from the compressedcondition shown in FIG. 3 to the extended condition of FIG. 2 indelivering the impact motion. To provide an appropriate spring length,the spring is received within a cylindrical recess 49 in the piston 46,and it ispreferable that the recess be of sufficiently small diameter toleave a considerable wall thickness for the piston to increase its mass,and therefore increase its inertia effect.

The control of the impact cylinder shown in the drawings is accomplishedby the selective admission of air pressure through either the port 50 orthe port 51. These parts lead into a crossbore in the head 30 whichdefines a control cylinder 52 carrying the control piston 53. A slot 54in the side of this piston receives the actuating pin 55 of the valvering 56. This ring is rotatably received within a suitable recess in thehead 30, and is held in place by the retaining ring 57, as best shown inFIG. 3. The pin 55 extends through a passage 58 communicating betweenthe control cylinder 52 and the recess receiving the ring 56. When airis admitted through the port 50, the control piston 53 moves to theposition of FIGS. 8 and 10, carrying with it the pin 55. This actionrotates the ring 56 into a position such that the holes 5963 are inalignment with the holes 64-68 in the head. This action serves toinstantly provide exhaust passages for air within the cylinder definedby the sleeve 32 to the left of the main piston 46.

The external air connections to the unit are preferably arranged so thatthe admission of air at the port 50 is simultaneous with the admissionof air pressure to the port 69 at the opposite end of the cylinderassembly. This results in the development of air pressure within therecess 49 in the main piston, which is communicated through the opening70 in the base of the cup 71 to the chamber 72 defined by the interiorof this cup. As this pressure develops, it reaches a level sufficient todrive the latch piston 73 to the right against the action of the latchspring 74, as air is vented out through the passage 75 in the head 31.The movement of the latch piston 73 to the right brings the conicalflange 76 into engagement with the conical inner portions 7780 of thedetent elements 8184. (Refer to FIG. 7.) The radial sections 85-88 ofthese elements extend through appropriately located openings in the wallof the cup 71 in sliding relationship, and movement of the controlpiston 73 from the FIG. 3 to the FIG. 2 position will result in radiallyretracting the portions 8588 as a result of the interengagement of theconical flange 76 with the portions 7780. The outer extremities of theportions 8588 are disposed to engage the shoulder 89 formed by thegroove 90 in the wall defining the recess 49 of the main piston.Withdrawal of the detents from this groove will release the piston 46for movement to the left under the combined etfect of the spring 48 andthe air pressure in the chamber 47. The opposite side of the piston hasbeen prepared for this movement by the placement of the valve ring 56 inthe exhaust position, as previously described.

Since it is desirable to obtain as much assistance from the air pressureas possible, the spring 74 functions primarily to establish apredetermined intensity of the chamber pressure back of the pistonbefore the latch system releases the piston. The amount of this releasepressure is determined by adjustment of the screw 91, the innerextremity of which serves as a seat for the spring 74. The stem 92 isslidable within the interior of the screw 91, with the latter being inthreaded engagement with the head 31. A retaining ring 93 secures thestem against outward movement as a result of air pressure, as the cup 71is fixed through threaded engagement with the head 31. The hollowinterior of the stem 92 provides an air passage into the chamber 47 andthe piston recess 49. To prevent leakage, the interior of the latchpiston 73 is sealed around the stem 92 by the O-ring 94, and passage outaround the periphery of the stem 92 through the bolt 91 is sealed by the"O"-ring 95. The periphery of the latch piston as it engages the cup 71is sealed by the -ring 96.

In order to prepare the cylinder assembly for the piston release and theresultant impact blow, pressure is admitted to the port 51 rather thanthe port 50. In other words, the pressure delivered to the port 51 isconsiderably in excess of that at the port 50. Under these conditions,the control piston 53 is moved to the FIG. 9 position, carrying theactuating pin 55 with it. This action rotates the valve ring to aposition in which the holes 59-63 are out of registry with the holes64-68, and the hole 97 assumes a position opposite the passage 58communicating with the control cylinder 52. In this position, thelateral hole 98 in the control piston 53 is also in alignment with thepassage 58, and the hole 98 communicates with the axial hole 99. Acomplete passage is thereby created which permits the air pressure to bedelivered through the port 51 to the interior of the main cylinder onthe left side of the piston 46, as shown in FIGS. 2 and 3. This pressureis delivered in sufficient intensity to compress the main spring 48, anddrive the piston to the FIG. 3 position. Conventional O"-ring seals at100 and 101 are provided to inhibit leakage around the main piston 46.The piston rod 45 is carried with the piston during this movementthrough the action of the retaining ring 102. As this movement continuesto its extreme point shown in FIG. 3, the edge defining the opening ofthe cylindrical recess 49 encounters the peripheral bevelled edges103-106 of the detent elements and forces them inwardly against theeffect of the latch mechanism, which had projected them to the FIG. 3position. This projection is induced by the movement of the latch piston73 to the left by the latch spring 74, which brings the conical surface107 in engagement with the inside surfaces of the portions 7780 of thedetent elements, sliding them outwardly. As the piston movementcontinues to its full extreme, the detent elements move into the groove89, as shown in FIG. 3. The unit is now ready for a reversal of airpressure to generate the action described previously, which will resultin movement from the FIG. 3 to the FIG. 2 position with a rapid impactblow.

The modified form of the invention shown in FIGS. 15 and 16 operates onthe same general principles, but with some variations in structuraldetail. The piston rod 107 traverses the head 108, and is connected tothe piston 109. A control piston 110 moves within a control cylinder 111in the head 108, in the manner previously described. Admission ofrelatively high-pressure to the conduit 112 results in releasing thepiston latch, and in placing the valve ring 113 in the exhaust position.This ring is identical to the ring 56 shown in FIG. 22. The arrangementof ports and openings in the head 108 and in the ring are the same asdescribed in connection with the previous modification. The T"-fitting114 serves the function of distributing the air pressure from theconduit 112 to the interior of the stem 115 and to the conduit extension116, which conducts the air pressure to the right side of the controlcylinder 111, as shown in FIGS. 15 and 16. In the cylindrical assemblyshown in FIGS. 15 and 16, the heads are in threaded engagement with thecylinder sleeve 117 with a modified form of the retaining ring beingshown at 118 to hold the valve ring 113 in position. The valve ring isalso rotatable with respect to the head 108, as previously described.

The principal difference between the modification shown in FIGS. 15 and16 and that shown in FIGS. 2 and 3 is in the latch mechanism. The stem119 is in threaded engagement with the cylinder head 120, and theenlarged end 121 of the stem retains an otherwise free cup 122. Theradial portions 123 and 124 of the semiannular detents 125 and 126 areinterposed axially, between the end of the cup 122 and the inner end ofthe cylinder head 120. The outermost edges of the detents 125 and 126are defined by a circumscribed diameter equal to or slightly less thanthe diameter of the cup 122. The conical portions 127 and 128 of thedetents 125 and 126, respectively, are received within the conical slot129 of the latch piston 130, thus inducing radial extension andretraction according to the movement of the piston along the latchcylinder 131 in the head 120. The upper portion of the cylinder 131 isvented at 132 to permit movement of the piston against the action of thespring 133. The hollow interior of the stem 115 admits pressure in thechamber 134, and the action of the projected radial sections 123 and 124is as described in connection with FIGS. 2 and 3. A port is provided at135 in the cup 122 to assure immediate transmission of air pressurebetween the main cylinder and the interior of the cup 122. The detents125 and 126 engage the shoulder provided by the groove 136 in the samemanner as previously described, thus retaining the main piston 109against the action of the spring 137.

Adjustment of the release pressure is accomplished by manipulation ofthe special nut 138, which is in threaded engagement with the stem 119.The adjusted position of the nut is maintained by the setscrew 139, androtation of the nut with respect to the stern will move the pins 140 and141, which traverse the head 120 and support the washer 142 acting as aseat for the spring 133. The stem 119 can either be in threadedengagement with the head 120, and locked in place by the nut 143, or thehold in the head 120 receiving the stem 119 may be large enough to clearthe threads. The presence of the nut 143 will serve to secure the stemin either case.

The particular embodiments of the present invention which have beenillustrated and described herein are for illustrative purposes only andare not to be considered as a limitation upon the scope of the appendedclaims. In these claims, it is my intent to claim the entire inventiondisclosed herein, except as I am limited by the prior art.

I claim:

l. A pneumatic actuator having a cylinder, a piston received forreciprocation within the cylinder, a piston rod connected to said pistonand traversing one end of said cylinder, wherein the improvementcomprises:

said piston having an axial pressure responsive surface receiving a mainspring;

latch means adapted to interengage said piston to a member normallyfixed with respect to said cylinder, said latch means being directlyresponsive to gas pressure admitted to the pressure responsive surfaceside of said piston to release said piston for movement in a selecteddirection;

valve means operatively associated with the said cylinder to selectivelyadmit pressure and provide exhaust on opposite sides of said piston; and

pneumatic conduit means providing pressure to said valve means. 7 v

2, An actuator as defined in claim 1, wherein said pressure responsivesurface is defined by an axial recess, and said latch means engages saidpiston at the surface defining said recess.

3. An actuator as defined in claim 2, wherein said piston has a shoulderon the said recess, and said latch means includes:

a cup normally fixed with respect to said cylinder, and axiallyreceivable in said piston recess, said cup having at least one openingin the periphery thereof;

a detent having a portion traversing said cup opening for reciprocationtherein in a direction having a radial component to releaseably engagesaid shoulder, said detent also having a portion within said cupinclined to the axis thereof;

a latch piston mounted for reciprocation in said cup, and

having axially spaced portions slideably receiving said detent inclinedportions;

latch biasing means urging said latch piston in a direction to projectsaid detent means to engaging position, said cup having port meansadmitting the surrounding pressure in said cylinder to the side of saidlatch piston corresponding to movement thereof to move said detent torelease position against the action of said latch biasing means; and

vent means in said cylinder for releasing pressure on the opposite sideof said latch piston.

4. An actuator as defined in claim 1, wherein said valve means includes:

a ring rotatably mounted in the opposite end of said cylinder from saidlatch means, said ring having at least one opening therein, saidcylinder having an exhaust passage in alignment with said opening in aselected angular position of said ring;

means in said opposite cylinder end defining a control cylinder, and apassage extending therefrom to said ring, said ring having an actuatingmember traversing said passage; and

a control piston slideably mounted in said control cylinder,

said control piston being interengaged with said ring projection wherebyreciprocation of said piston induces reciprocating rotary movement ofsaid ring between said selected angular position and a position in whichan opening in said ring is disposed in alignment with means forming anintake passage communicating with said cylinder.

5. An actuator as defined in claim 4, wherein said intake passageincludes said control cylinder on one side of said control piston.

1. A pneumatic actuator having a cylinder, a piston received forreciprocation within the cylinder, a piston rod connected to said pistonand traversing one end of said cylinder, wherein the improvementcomprises: said piston having an axial pressure responsive surfacereceiving a main spring; latch means adapted to interengage said pistonto a member normally fixed with respect to said cylinder, said latchmeans being directly responsive to gas pressure admitted to the pressureresponsive surface side of said piston to release said piston formovement in a selected direction; valve means operatively associatedwith the said cylinder to selectively admit pressure and provide exhauston opposite sides of said piston; and pneumatic conduit means providingpressure to said valve means.
 2. An actuator as defined in claim 1,wherein said pressure responsive surface is defined by an axial recess,and said latch means engages said piston at the surface defining saidrecess.
 3. An actuator as defined in claim 2, wherein said piston has ashoulder on the said recess, and said latch means includes: a cupnormally fixed with respect to said cylinder, and axially receivable insaid piston recess, said cup having at least one opening in theperiphery thereof; a detent having a portion traversing said cup openingfor reciprocation therein in a direction having a radial component toreleaseably engage said shoulder, said detent also having a portionwithin said cup inclined to the axis thereof; a latch piston mounted forreciprocation in said cup, and having axially spaced portions slideablyreceiving said detent inclined portions; latch biasing means urging saidlatch piston in a direction to project said detent means to engagingposition, said cup having port means admitting the surrounding pressurein said cylinder to the side of said latch piston corresponding tomovement thereof to move said detent to release position against theaction of said latch biasing means; and vent means in said cylinder forreleasing prEssure on the opposite side of said latch piston.
 4. Anactuator as defined in claim 1, wherein said valve means includes: aring rotatably mounted in the opposite end of said cylinder from saidlatch means, said ring having at least one opening therein, saidcylinder having an exhaust passage in alignment with said opening in aselected angular position of said ring; means in said opposite cylinderend defining a control cylinder, and a passage extending therefrom tosaid ring, said ring having an actuating member traversing said passage;and a control piston slideably mounted in said control cylinder, saidcontrol piston being interengaged with said ring projection wherebyreciprocation of said piston induces reciprocating rotary movement ofsaid ring between said selected angular position and a position in whichan opening in said ring is disposed in alignment with means forming anintake passage communicating with said cylinder.
 5. An actuator asdefined in claim 4, wherein said intake passage includes said controlcylinder on one side of said control piston.